[ lahyt-fast, -fahst ]

  1. not affected or faded by light, especially sunlight; colorfast when exposed to light.

Origin of lightfast

First recorded in 1955–60; light1 + fast1

Other words from lightfast

  • lightfastness, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use lightfast in a sentence

  • He harnessed four horses, who could quickly traverse the plain, and entered his light fast carriage.

  • It was growing light fast now, and they strained their eyes for a sail.

    The Rival Campers | Ruel Perley Smith
  • Their light fast mobile units scoot right on past the heavily fortified centers and capture small positions in the rear.

    Dave Dawson at Dunkirk | Robert Sydney Bowen
  • "It is getting light fast," Dick said, as he wiped the perspiration from his face.

    The Tiger of Mysore | G. A. Henty
  • It was growing light fast, and it was time they were on their way.

    Battling the Clouds | Captain Frank Cobb

British Dictionary definitions for light-fast


  1. (of a dye or dyed article) unaffected by light

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012